1. Field of the Invention
The present invention relates to an image shake correcting apparatus, and more particularly to an image shake correcting apparatus for correcting (preventing) shakes of images picked up by a camera.
2. Description of the Related Art
Known image shake correcting apparatuses for use in television cameras include one in which an anti-shake lens is movably arranged in a photographic optical system within a plane orthogonal to the optical axis and, when any vibration works on the camera (the photographic optical system of the camera), the anti-shake lens is driven by an actuator in a direction to cancel that vibration to correct any image shake that may occur. In such an image shake correcting apparatus, the vibration working on the camera is detected by a shake detection sensor (angular velocity sensor, acceleration sensor or the like), and the displacement of the anti-shake lens is determined to correct the image shake on the basis of a signal supplied from that shake detection sensor (see Japanese Patent Application Laid-Open No. 2002-229089 for instance).
Incidentally, shake signals issued by the shake detection sensor may include not only signals warning against vibrations to be corrected, such as accidental manual shakes but also signals resulting from the photographer's intentional camera manipulation, such as panning or tilting. Therefore, if the anti-shake lens is driven merely in response to a shake signal, image shake correction will be done even when the camera is panned or tilted on purpose. However, unpreferably, if image shake correction is done against panning/tilting, an image shake (reactionary shake) will occur after the panning/tilting is ended, inviting an odd feeling in the camera operation or the image picked up.
In view of this problem, a way of correcting such a reactionary shake is proposed, in which it is automatically judged whether or not a shake signal issued by the shake detection sensor is due to panning/tilting. If the signal is judged to be due to panning/tilting, the image shake correction is stopped, the anti-shake lens is returned to the center of its movable range (the reference position where the displacement is 0) and kept there unmoving (see Japanese Patent Application Laid-Open No. 5-142614 for instance).
It has to be noted that, at the end of panning/tilting, the pertinent shake signal does not immediately fall to exactly zero but gradually approaches zero on account of an abrupt change in the angular velocity or acceleration of the camera, a residual signal in a capacitor in the circuit or the like. Consequently, when image shake correction is resumed, the anti-shake lens is substantially moved by this shake signal, resulting in a reactionary shake of the image. Such a reactionary shake makes impossible accurate and prompt framing.
As a technique to prevent such a reactionary shake, Japanese Patent Application Laid-Open No. 10-213832 discloses an optical device with an image shake correcting function, provided with gain altering means which alters the gain of the shake output signal in response to the detection of the end of panning. Incidentally, the technique disclosed in this Japanese Patent Application Laid-Open No. 10-213832 is to alter the gain of the shake output signal, and differs in the concept of configuration from the present invention.